Determining a location based on radio frequency identification (RFID) read events

ABSTRACT

Techniques for determining an item location based on multiple RFID parameters from multiple read events are described. In an example, a computer system may access a first read event. A first RFID reader located within a first zone may have generated the first read event at a first time. The first read event may identify an RFID tag and may include first RFID parameters. The computer system may access a second read event. A second RFID reader located within a second zone may have generated the second read event at a second time within a predefined amount of time from the first time. The second read event may identify the RFID tag and include second RFID parameters. The computer system may determine whether the item location falls within the first zone or the second zone based on two or more first RFID parameters and two or more second RFID parameters.

BACKGROUND

Radio frequency identification (RFID) technology has been adopted inmany industries for different applications. For example, RFID isdeployed to track locations of items in an operational environment. Inparticular, an RFID tag is attached to an item. An RFID reader isoperated to read the RFID tag. Based on reading the RFID tag, adetermination is made that the item is located in proximity to the RFIDreader.

In many operational environments, the RFID tag of the item may be readby multiple RFID readers within a certain period of time. In a way, theRFID readers cross-read the RFID tag at substantially the same time.Hence, processing the different reads of the different RFID readers maybe performed to determine which of the RFID readers is closest to theitem and, accordingly, complete the proximity detection.

Generally, processing the cross-reads to detect proximity involvesdetermining the maximum received signal strength. For example, aparticular RFID reader measuring the largest received signal strengthindicator (RSSI) is selected as being the closest to the item. However,such a proximity detection may be inaccurate. For example, radiofrequency (RF) reflections and obstructions from objects and orientationof the RFID tag relative to the RFID readers may result in the largestRSSI, whereas the particular RFID reader may not be the closest readerto the item.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments in accordance with the present disclosure will bedescribed with reference to the drawings, in which:

FIG. 1 illustrates an example operational environment for trackingitems, according to an embodiment of the present disclosure;

FIG. 2 illustrates an example of two RFID readers reading an RFID tagattached to an item, according to an embodiment of the presentdisclosure;

FIG. 3 illustrates an example block diagram for processing read eventsof multiple RFID readers to determine whether an item may be locatedwithin a zone associated with one of the RFID readers, according to anembodiment of the present disclosure;

FIG. 4 illustrates an example flow for analyzing multiple read eventsand accordingly determining the closest RFID reader to an item,according to an embodiment of the present disclosure;

FIG. 5 illustrates another example flow for analyzing multiple readevents based on a map of the RFID readers, according to an embodiment ofthe present disclosure;

FIG. 6 illustrates an example statistical analysis of multipleparameters across multiple read events, according to an embodiment ofthe present disclosure; and

FIG. 7 illustrates example end-to-end architecture of a computingenvironment for processing RFID read events, according to an embodimentof the present disclosure.

DETAILED DESCRIPTION

In the following description, various embodiments will be described. Forpurposes of explanation, specific configurations and details are setforth in order to provide a thorough understanding of the embodiments.However, it will also be apparent to one skilled in the art that theembodiments may be practiced without the specific details. Furthermore,well-known features may be omitted or simplified in order not to obscurethe embodiment being described.

Embodiments herein are directed to improving accuracy of detectingproximity between an item and an RFID reader. The proximity may indicatehow close a location of the item may be relative to a location of theRFID reader, or vice versa. In an example, an RFID tag may be attachedto the item and may store information about the item. During a readcycle, the RFID reader may transmit a number of RF interrogation signalsand receive a number of RF responses thereto from the RFID tag. A readevent may be generated from the RF interrogation and response. Forexample, the read event may identify the item from the informationstored in the RF tag and may include multiple RFID parameters measuredduring the reading cycle (generally referred to herein as “parameters”).These parameters (e.g., RFID parameters) may include a count of how manytimes the RFID tag was read (e.g., the number of RF responses), anaverage received signal strength, the maximum received signal strength,time stamps of the RF response signals, electrical angle, and/or otherRF-related parameters.

A back-end system may receive RF read events from multiple RFID readers.Some of the read events may identify the same item and may have beengenerated within a predefined period of time (e.g., a short period oftime relative to movement of the item or during overlapping readcycles). The back-end system may analyze these read events to determinewhich of the applicable RFID readers is in closest proximity to theitem. Generally, to mitigate the risk of cross-reads, the analysis mayinvolve multiple parameters (e.g., at least two) from each of the readevents. Because multiple parameters may be analyzed, the accuracy of theproximity detection may be improved.

To illustrate, consider an example of an item labeled with an RFID tagand placed on a conveyor belt. The conveyor belt may move the itemwithin a sortation facility, through an exit door, and onto a deliveryvehicle. An RFID reader may be located at the exit door to track andensure that the item is destined to the correct delivery vehicle. TheRFID reader may cover a zone around the exit door. The RFID tag may beread when the item moves within the zone. In this illustrative example,another RFID reader may also be located at an adjacent exit door and maycover an area around the adjacent exit door. Because the two RFIDreaders are adjacent to each other and because of a number of otherfactors (e.g., overlap between the two zones, RF reflection, RFobstruction, relative orientation of the RFID tag to the two RFIDreaders), both RFID readers may simultaneously, or nearlysimultaneously, read the RFID tag as the item leaves the sortationfacility through the first exit door. Hence, there may be a risk ofinaccurately tracking the location of the item to the adjacent exitdoor. To mitigate this risk and improve the accuracy, a back-end systemmay analyze relevant read events of the two RFID readers. For example,parameters from a first read event of the first RFID reader may benormalized based at least on parameters from a second read event of theadjacent RFID reader, and vice versa, to generate scores for each of thetwo read events. The back-end system may compare the scores to identifywhich of the two zones may contain the item. For instance, the count ofhow many times the RFID tag was read, the average signal strength, andthe maximum signal strength from the first read event may be normalizedusing the total count, the total average signal strength, and the totalmaximum signal strength across the two read events. These normalizedparameters are summed to generate the score for the first read event. Asimilar process may be used to generate the score for the second readevent. The back-end system may determine that the item may be locatedwithin the zone corresponding to the RFID reader that earns the highestscore.

In the interest of clarity of explanation, various embodiments of thepresent disclosure are described in connection with an illustrativeexample of an RFID tag read by two RFID readers, where the RFID tag maybe attached to a movable item and where the RFID readers may bestationary. However, the embodiments are not limited as such. Forexample, the embodiments may similarly apply to a larger number of RFIDreaders. In this case, a back-end system may analyze relevant readevents generated by these RFID readers. In another example, the item maybe stationary and the RFID readers may be movable. In this example, adetermination may be made as to which of the RFID readers is mostproximate to the stationary location of the item. In yet anotherexample, a single RFID reader may read multiple RFID tags attached torespective items. In this example, a determination may be made as towhich of the items is most proximate to the RFID reader. Each of theread events may correspond to a read by the RFID reader of a respectiveRFID tag.

FIG. 1 illustrates an example operational environment for trackingitems. Generally, the operational environment may include a number ofRFID readers in communication with a back-end system. Each RFID readermay be located within a known location of the operational environmentand cover a zone around the known location. An RFID tag may be attachedto an item. The item may be moved between zones covered by the RFIDreaders. Generally, as the item arrives into and moves within a zone, anRFID reader covering the zone may read the RFID tag during various readcycles. Once the item leaves the zone, the RFID reader may no longerread the RFID tag. In certain situations, however, the RFID reader mayread the RFID tag even when the item is outside the zone and/or anotherRFID reader(s) may read the RFID tag as the item progresses through thezone. To mitigate the risk of inaccurately tracking the item, theback-end system may analyze multiple read events that identify the item.

FIG. 1 illustrates two example RFID readers, shown as RFID reader 110and RFID reader 120. The RFID reader 110 may be located at an exit doorof a sortation facility to cover a zone 112 around the exit door. Hence,an item 140 going through the zone 112 may be detected. For example, anRFID tag 142 may be attached to the item 140. The item 140 may be placedon a conveyor belt 144 going through the exit door. As the itemprogresses through the zone 112, the RFID reader 110 may read the RFIDtag 142 during a read cycle. Accordingly, the RFID reader 110 maygenerate and send a read event 114 to the back-end system 130.

Similarly, the RFID reader 120 may be located at an adjacent exit doorto cover an adjacent zone 122. There may be an overlap between the twozones 112 and 122. The RFID reader 120 may generate and send read eventsfor items progressing through the zone 122 to the back-end system 130.However, in certain situations, the RFID reader 120 may also cross-readthe RFID tag 142 while the item 140 is on the conveyor belt 144 and isprogressing through the other zone 112. For example, the item 140 may betoo close or within the overlap between the two zones 112 and 122.Additionally or alternatively, various reasons may cause this readeffect including, for instance, RF reflection from other objects in theoperational environment and/or relative orientation of the RFID tag 142to RFID reader 120. Accordingly, the RFID reader 120 may generate andsend, to the back-end system 130, a read event 124 corresponding to thereading of the RFID tag 142 during the read cycle of the RFID reader120.

The back-end system 130 may receive and analyze the read event 114 andthe read event 124 to track the item as being located within the zone112 and not the zone 122. The analysis may use multiple parameters fromeach of the read events as further described in the next figures.Generally, the analysis may involve a normalization of certainparameters.

In an example, the back-end system 130 may be a server or any othercomputing system suitable for receiving read events from RFID readersover a wireless or wired communication network. For instance, theback-end system 130 may include computing hardware or a virtual instancerunning on computing hardware (e.g., a cloud-based computing service).In addition, the back-end system 130 may be configured to host atracking module 132.

The tracking module 132 may be configured to analyze read events andaccordingly track item locations. The tracking may be in real time orsubstantially real time. Real time may be defined as a predefinedtimeframe relative to the timing of the read events, where the trackingmay be considered up to date and not stale if processed within thepredefined timeframe. For example, the predefined timeframe may be setas five minutes, as a function of the processing time needed to performthe tracking analysis, or as a function of an RFID reader's read cycle(e.g., the tracking may be in real time if the read event corresponds tothe last read cycle and no new read events have been generated by theRFID reader). In an example, upon the back-end system 130 receiving thefirst read event 114 and the second read event 124, the tracking module132 may determine that the two read events identify the same item 140.Next, the tracking module 132 may determine that the two read events mayhave been generated around the same time (e.g., there is some timeoverlap or being generated within a threshold amount of time of eachother). Accordingly, the tracking module 132 may further analyze atleast two parameters from the first read event 114 and at least twoparameters from the second read event 124 and determine that the item140 may be located within the first zone 112 and not the second zone114.

In addition, tracking item locations may include providing or reportinglocation information to client devices. For instance, a client devicemay be subscribed to a tracking service of the tracking module 132. Thetracking module 132 may push or, upon request, transmit the locationinformation to the client device. Further, the tracking module 132 maydrive a user interface of the client device. The location informationmay be presented at the user interface. For instance, the user interfacemay also allow a user to browse location information per item or perRFID reader. Hence, the user interface may present the current locationand/or location history of the item 140 as the item 140 progressesthrough the sortation facility. The user interface may also present alist of items detected as having progressed or currently progressingthrough the zone 112 of the RFID reader 110 and the related timinginformation. In addition, the user interface may present a map of thesortation facility. The map may show the locations of the RFID readers,identify items, and present the detected item locations.

FIG. 2 illustrates an example of two RFID readers 210 and 220 reading anRFID tag 232 attached to an item 230. The RFID readers 210 and 220 maycover zones 212 and 222, respectively. As the item 230 moves, the item230 may progress through one of the two zones 212 and 222 or through anoverlap 240 between the two zones 212 and 222. During a read cycle ofthe RFID reader 210, the RFID reader 210 may read the RFID tag 232depending on the location of the item 230 relative to the zone 212 (or,equivalently, relative to the location of the RFID reader 210) andvarious factors (e.g., orientation of the RFID tag 232, RF reflection,RF propagation, etc.). If the RFID tag 232 is read, the RFID reader 210may generate a read event. The read event may include information aboutthe item 230 and RF-related parameters. Similarly, the RFID reader 220may read the RFID tag 232 during a read cycle of the RFID reader 220 andmay generate a read event. This read event may correspond to across-read of the RFID tag 232.

In an example, the read cycles of the RFID readers 210 and 220 need notbe the same. Each read cycle may involve a number of transmitted RFsignals and a number of RF responses thereto (e.g., an RF signalreflected back and received based on a transmitted RF signal). Hence,within a read cycle, the RFID tag 232 may be read a number of times. Inaddition, the timing of the read cycles need not be synchronized for thetwo RFID readers 210 and 220.

A zone (e.g., each of the zones 212 and 222) may represent a volume ofspace within which an RFID tag may be read. The volume may be defined bythe intensity and frequency of transmitted RF signals, objects in theoperational environment, specific geometry and properties of theoperational environment, and other RF-related factors. Generally, theRFID reader may be located within the volume (e.g., at about thecenter). FIG. 2 illustrates ellipsoidal zones, but other shapes may bepossible.

In an example, the RFID tag 232 may be adhesively attached to the item230 or to a container containing the item 230. In an example, the RFIDtag 232 may be a passive RFID tag or an active RFID tag. Regardless ofthe tag type, the RFID tag 232 may store information about the item 230.The information may identify the item 230. For instance, a uniqueidentifier such as an electronic product code (EPC), a universal productcode (UPC), or some other serial number unique to the item 230 may beencoded in the RFID tag 232 according to an encoding standard, such asglobal standards one (GS1). The information may also provide additionalinformation regarding the origin, destination, and/or handling of theitem 230.

A read event may include any of the information about the item 230(e.g., the identifying information). In addition, the read event mayinclude information about the RFID reader that generated the read event.This information may include, for instance, a unique identifier and,optionally, a location of the RFID reader. Further, the read event mayinclude measured RF-related parameters such as the count of times theRFID tag 232 may have been read during the relevant read cycle, theaverage RSSI, the maximum RSSI, and time stamps of the RF responses.

Generally, RFID refers to a wireless, non-contacting system fortransferring data by way of radio frequency electromagnetic fields. Inan RFID system, data transfers occur in the form of modulated signalstransmitted between an RFID tag (or an RFID device), which may includevarious communication components, logic or circuitry, and an RFIDreader, which may include antennas or other like devices. Data storedwithin a microchip or other storage device associated with the RFID tagmay be sent to the RFID reader, which may interpret not only the datareceived in the RFID signal, but also other relevant information orattributes of the RFID signal, such as an intensity or a frequency ofthe RFID signal, as well as a direction from which the RFID signaloriginated, a range traveled by the RFID signal or at least some of theinformation or data included in the RFID signal. The transfer of theRFID signal is initiated when an electromagnetic field transmitted by anRFID reader is sensed by an RFID tag, which transmits information ordata that may be stored in association with the RFID tag in one or moremicrochips or other storage devices.

RFID systems provide a number of advantages over similar systems for theshort-range transfer of information or data. First, an RFID tag may beformed of components having remarkably small, compact shapes and sizes,and tags that are as thin as a sheet of paper or smaller than a grain ofrice are quite common. Additionally, unlike a bar code (e.g., aone-dimensional bar code or a two-dimensional “QR” code), an RFID tagneed not be provided within a line of sight of an RFID reader in orderto successfully transmit data. Therefore, RFID tags may be concealed orembedded into many different types of objects of any size or shape, aswell as humans or other animals. Next, an RFID tag may be programmedwith a fixed set or packet of “read-only” data which may be transmittedto an RFID reader countless number of times in theory, or reprogrammedwith modifiable sets of data that may be written and rewritten, asneeded, based on the application in which the RFID tag is provided.Moreover, and perhaps most importantly, while an active RFID tagincludes and utilizes a local power source, such as a battery, a passiveRFID tag does not require any power in order to successfully transmit aset or packet of data to an RFID reader, and may therefore transmit suchdata when power supplies are unavailable or in environments whereproviding power to the RFID tag is infeasible.

RFID signals may be transmitted from an RFID tag to an RFID reader inmany different formats and at many different frequency levels. An RFIDtag that transmits signals within low frequency (LF), medium frequency(MF), or high frequency (HF) levels (e.g., approximately 3 kilohertz to30 megahertz, or 3 kHz-30 MHz) may transfer relatively small-sized setsor packets of data over short ranges (e.g., between ten and one hundredcentimeters, or 10-100 cm). Other RFID tags may transmit signals athigher frequency levels, such as ultrahigh frequency (UHF) or microwavelevels (e.g., approximately 300 megahertz to 300 gigahertz, or 300MHz-300 GHz) including larger sets or packets of data at ranges of onemeter (1 m) or longer.

A signal transmission from an RFID tag to an RFID reader may be achievedin any number of ways. An inductively coupled RFID tag is an RFID tagthat is powered by energy obtained from magnetic fields generated by anRFID reader, and may be coupled to the RFID reader using this energy. Inthis regard, an RFID reader may include one or more coils through whichan electric current may pass, thereby causing a magnetic field to begenerated by the RFID reader according to Ampere's Law. Likewise, aninductively coupled RFID tag may also include one or more coils. Whenthe RFID tag passes within a particular range of the RFID reader, anelectric current is generated within the coils of the RFID tag, therebycoupling the RFID reader and the RFID tag based on the magnetic fluxpassing through the respective sets of coils. The electric currentpassing through the coils of the RFID tag may then power internalcircuits within the RFID tag and cause an RFID signal to be transmittedfrom the RFID tag to the RFID reader accordingly. Thus, inductivelycoupled RFID tags are commonly used in powerless environments where apassive system for transmitting signals may be required.

Additionally, an RFID tag may be coupled by any number of other modes.For example, capacitively coupled RFID tags include coupling plates thatare designed to correspond to a plate of an RFID reader. When the RFIDtag is placed in sufficiently close proximity to the RFID reader,thereby causing the corresponding coupling plates of the RFID tag andthe RFID reader to be aligned in parallel with one another and within ashort range, a transfer of data from the RFID tag to the RFID reader isachieved. Unlike an inductively coupled RFID tag, which is powered by amagnetic field generated by an RFID reader, a capacitively coupled RFIDtag is powered by an alternating electric field generated by an RFIDreader. For this reason, capacitively coupled RFID tags usually havemore limited operating ranges than inductively coupled RFID tags and aretypically employed in near-field communication environments. Similarly,a backscatter-coupled RFID tag receives power emitted from an RFIDreader's antenna. A portion of the emissions from the RFID reader isreceived by a corresponding antenna of the RFID tag and may be filteredor rectified, as necessary, in order to trigger a transfer of data fromthe RFID tag to the RFID reader. Any type or mode of coupling between anactive, semi-active (e.g., powered on a temporary basis or for limitedpurposes) or passive RFID tag and an RFID reader may be utilized inaccordance with the present description.

In addition to RFID tags which are automatically coupled with an RFIDreader, the systems and methods of the present description may furtherinclude an RFID tag, such as a passive RFID tag, which may be manuallyactivated, e.g., coupled upon a manual action, by a human or machine inorder to cause a transmission of a data signal from the RFID tag to oneor more RFID readers. A manually activated RFID tag may include physicalor virtual switches that may close a circuit within the RFID tag andthereby permit the RFID tag to function as a data transmitter in thepresence of an electric or magnetic field. For example, a manuallyactivated RFID tag may include capacitive elements that define acapacitor within the RFID tag and may effectively close a circuit withinthe RFID tag when such elements detect bioelectricity from a user. Theterm “bioelectricity” generally refers to electrical charges or electricfield gradients that may be stored within a living body, such as a humanbody, which contains blood and other matter having a variety ofpositively and negatively charged ions (e.g., sodium, chloride andothers). Bioelectricity within a body may cause a change in capacitanceof such elements in a vicinity of a location touched by the body (e.g.,a digit such as a finger or thumb), due to disruptions in electricalfields caused by the body's presence, thereby further causing a changein the time constant of the RFID tag, and a discharge of the capacitorin an amount that may be defined as a function of the resistance of thecapacitive elements.

According to some embodiments, such capacitive elements may be formedinto a layered stack or may include a substantially linear or planar gapor break, and may be covered with a flexible protective layer formedfrom one or more plastics or rubbers (e.g., acrylics, vinyls,polyurethanes, or the like), or other like materials. The protectivelayer may be adhered to one or more capacitive elements of an RFIDcircuit, which may include elements formed from a conductive materialsuch as aluminum, copper, silicon, or indium tin oxide that areseparated by an air gap. When a user touches a protective layer of anRFID tag with a finger, which is a bioelectric conductor, a change inthe effective capacitance (on the order of approximately one picofarad)between the elements, which are also conductors, in a vicinity of apoint or points of contact with the protective layer, is introduced.Such contact forms a conductive bridge across the elements, therebycausing disruptions in electrical fields in the vicinity of one or moreof the elements, and further causing an internal current flow throughthe RFID tag circuit.

In addition to capacitive elements, a circuit of an RFID tag may includeother components for enabling a manual actuation thereof by a human or amachine, including one or more substantially planar conductive elementsthat may be separated by an air gap. Such an air gap between theconductive elements defines an open switch within the circuit of theRFID tag, which may also be covered with a flexible protective layerthat may be formed from one or more plastics, rubbers, or other likematerials. When a user contacts an external surface of the RFID tagcorresponding to the air gap, e.g., the flexible protective layer overthe air gap, at least two of the conductive elements are placed incontact with one another, thereby bridging the air gap between theconductive elements and closing the open switch. Subsequently, aninternal current flow through the RFID tag circuit is enabled. Becausethe bridging of the air gap and the closure of the open switch isregistered by manually driven electrical contact, a manually activatedRFID tag including substantially planar conductive elements does notrequire bioelectricity in order to operate properly, and a user mayinteract with the RFID tag using not only his or her fingers or hands(which may be gloved or ungloved), but also a stylus, a pointer oranother like object.

FIG. 3 illustrates an example block diagram for processing read eventsof multiple RFID readers to determine whether an item may be locatedwithin a zone associated with one of the RFID readers. In thisillustrative example, multiple parameters across multiple read eventsare analyzed to mitigate the risk of cross-read and more accuratelydetermine the location of the item. Generally, the processing mayinvolve normalizing the parameters across the read events, generatingscores for the read events from the normalization, and comparing thescores.

In the particular illustrative example of FIG. 3, two read events, eachhaving four parameters, may be analyzed. A first RFID reader may beassociated with a first zone 310, may read an RFID tag during a readcycle, and may generate a first read event. Similarly, a second RFIDreader may be associated with a second zone 320, may read the RFID tagduring a read cycle, and may generate a second read event. The two readevents may be generated within a short period of time of each other. Forinstance, the two read cycles may overlap entirely or partially in time.Each of the read events may include measured values for four parameters:count of times, average signal strength (e.g., RSSI), maximum signalstrength, and time stamps. In particular, two read events are generatedby two RFID readers, respectively.

In this illustration, the first read event may include a first count 312(shown with a value of ten), a first average RSSI 314 (shown with avalue of one hundred), a first maximum RSSI 316 (shown with a value ofone thousand), and a first last time stamp 318 (shown with a value T1).The last time stamp 318 may correspond to the last received RF signalduring the read cycle. Similarly, the second event may include a secondcount 322 (shown with a value of twenty), a second average RSSI 324(shown with a value of two hundred), a second maximum RSSI 326 (shownwith a value of two thousand), and a second last time stamp 328 (shownwith a value T2).

The analysis of the two read events may include a normalization of someof the parameters. For example, a total count may be generated by addingthe first count 312 and the second count 322. The first count 312 may benormalized by dividing the first count 312 by the total count, resultingin a first normalized count (shown with a value of 0.333). A similarnormalization may be performed for the second count 322 to generate anormalized second count (shown with a value of 0.667). Thisnormalization may also be performed for the average RSSIs and themaximum RSSIs resulting in a first normalized RSSI (shown with a valueof 0.333) and a first normalized maximum RSSI (show with a value of0.333) for the first read event, and a second normalized RSSI (shownwith a value of 0.667) and a second normalized maximum RSSI (shown witha value of 0.667) for the second read event.

Next, the analysis may include generating a score per read event basedon the respective normalized parameters. For example, normalizedparameters corresponding to a zone (or, equivalently, to a RFID reader)may be summed 340. Hence, a first score for the first event may begenerated by adding the first normalized count, the first normalizedaverage RSSI, and the first normalized maximum RSSI (the first score isshown with a value of one). Similarly, a second score for the secondevent may be generated by adding the second normalized count, the secondnormalized average RSSI, and the second normalized maximum RSSI (thesecond score is shown with a value of two).

Further, the analysis may compare the scores of the read events.Depending on the results of the comparison, a determination may be madeas to which of the RFID readers is closest to the item. Continuing withthe previous example, a comparison 350 of the first score and the secondscore may indicate that the second score is larger. Accordingly, theitem may be identified as progressing through the second zone 320 andthereby the second RFID reader is the closest 354. On the other hand, ifthe comparison 350 may have resulted in the opposite indication, thefirst RFID reader may be determined as being the closest 352.

In certain situations, the scores may fall within a threshold amount ofeach other. For example, the scores may be equal or may be too close(e.g., deviating within a predefined margin of plus or minus fivepercent, or some other predefined deviation). In such situations, theanalysis may further involve other parameters from the read events.These parameters may include time stamps. For example, the first lasttime stamp 318 and the second last time stamp 328 may be compared 360 todetermine a timing order between the two. If the first last time stamp318 is the latest of the two, the first RFID reader may be determined asbeing the closest 352. Otherwise, the second RFID reader may bedetermined as being the closest 354.

The above analysis is provided for illustrative purposes. Generally, atleast two parameters per read event may be analyzed. Likewise, otherstatistical analysis (e.g., beyond normalization and comparison) mayalso be used. In addition, the analysis may be repeated for more thantwo read events and/or for more than two RFID readers, when such eventsfall within a predefined period of time from each other (e.g., byoverlapping partially or fully).

Turning to FIGS. 4-6, the figures illustrate example flows for analyzingmultiple read events to identify proximity of an item labeled with anRFID tag to RFID readers. A computer system is illustrated as performingoperations of the example flows. In an example, the computer system mayrepresent a back-end system hosting a tracking module (e.g., theback-end system 130 hosting the tracking module 132 of FIG. 1).Generally, the computer system may include a processor and a memorycoupled to the processor. The processor may execute computer-readableinstructions stored in the memory. The computer-readable instructionsmay include instructions for performing the operations.

In the interest of clarity of explanation, the analysis of read eventsof two RFID readers may be described in connection with the exampleflows. However, the example flows may similarly apply to a larger numberof read events from two or a larger number of RFID readers. Inparticular, if a read event identifies the item and falls within apredefined time period of the analysis (e.g., overlaps with other readevents being analyzed), the read event may be considered in theanalysis. Accordingly, the relevant parameters from this read event arefurther analyzed.

Some of the operations of the example flows of FIGS. 4-6 may be similar.Such similarities are not repeated herein in the interest of clarity ofexplanation. Also, while the operations are illustrated in a particularorder, it should be understood that no particular order is necessary andthat one or more operations may be omitted, skipped, and/or reordered.

FIG. 4 illustrates an example flow for analyzing multiple read eventsand accordingly determining the closest RFID reader to the item. Theexample flow may start at operation 402, where the computer system mayaccess a first read event of a first RFID reader. The first RFID readermay read the RFID tag during a first read cycle of the first RFID readerand accordingly generate the first read event. The first read event mayinclude a number of first parameters, such as a first count of times theRFID tag was read, a first average signal strength, a first maximumsignal strength, and a first set of time stamps. Multiple mechanisms maybe possible to access the first read event. For example, the computersystem may poll (e.g., send a request and receive a response) the firstRFID reader and receive the first read event based on a polling cycle.In another example, a push mechanism may be implemented, where as soonas generated, the first RFID reader transmits the first read to thecomputer system. Under this approach, the first read event may bereceived in real time or substantially real time.

At operation 404, the computer system may access a second read eventfrom a second RFID reader. The access may use a polling or a pushingmechanism. The second RFID reader may read the RFID tag during a secondread cycle of the second RFID reader and accordingly generate the secondread event. The second read event may include similar parameters, suchas a second count of times the RFID tag was read, a second averagesignal strength, a second maximum signal strength, and a second set oftime stamps.

At operation 406, the computer system may determine whether the readevents were generated within a predefined amount of time from eachother. In an example, the computer system may determine if an overlapbetween the first read cycle and the second read cycle exists. If theoverlap exists, the computer system may determine that a cross-read ofthe RFID tag may exist. That may be the case because both RFID readersmay have read the RFID tag, when only one should have. For instance, ifeach read cycle is five seconds long and there is an overlap of twoseconds, then both RFID readers may have simultaneously read the RFIDtag during these two seconds. In another example, the predefined amountof time may be set as a threshold time period. The threshold time periodmay be a function of the speed at which the item may be moving. Thefaster the speed may be, the smaller the threshold time period may be.In both examples, if the computer system determines that the first andsecond read events fall within the predefined amount of time, thecomputer system may determine that there is a cross-read. Accordingly,operation 408 may be performed to mitigate this risk by analyzingmultiple parameters from each of the read events. Otherwise, operation410 may be performed.

At operation 408, the computer system may determine a location of theitem based on at least two parameters from the first event and at leasttwo parameters from the second event. The location may be representproximity to the closest RFID reader or the item moving through a zonecovered by the RFID reader. The computer system may use a combination ofany of the parameters (e.g., counts, average signal strengths, maximumsignal strengths, time stamps) across the read events. Generally, thecomputer system may implement a statistical analysis. The statisticalanalysis may involve scoring each read event, where the score whencompared to other scores may indicate a potential or a likelihood of thelocation of the item relative to the location and/or zone of therespective RFID reader. In an example, the statistical analysis mayinclude a normalization to generate normalized scores, a summation togenerate total scores per read event, a comparison of the total scores,and a comparison of last time stamps as illustrated in FIG. 3.

At operation 410, the computer system may determine the location of theitem based on one of the read events. Because the read events may begenerated at different times such that the risk of cross-read is low,the computer system may analyze the read events separately. The analysismay use one or more of the parameters. For instance, upon accessing thefirst read event, the computer system may use any of the first count,the first average signal strength, the first maximum signal strength,and/or the first set of time stamps to determine that during the firstread cycle, the item may be closest to the first RFID reader. Similarly,upon accessing the second read event, the computer system may use any ofthe four parameters to determine that during the second read cycle, theitem may be closest to the second RFID reader.

At operation 412, the computer system may provide information about thelocation of the item. For example, the computer system may drive a userinterface of a client device. The user interface may present thelocation of the item in real time or substantially real time or ahistory of the location as the item moves between different zones.

FIG. 5 illustrates another example flow for analyzing multiple readevents based on a map of the RFID readers. The example flow may start atoperation 502, where the computer system may receive the first readevent from the first RFID reader. In an example, the first read eventmay be received over a data communication network between the computersystem and the first RFID reader.

At operation 504, the computer system may access the map of RFIDreaders. The map may be stored locally at or may be remotely availableto the computer system. Accordingly, the computer system may retrievethe map from local memory or from a remote storage device. The map mayidentify and show the locations of the RFID readers and/or may showzones covered by the RFID readers.

At operation 506, the computer system may identify the second RFIDreader based on the map and the first read event. For example, the firstread event may identify (e.g., include a unique identifier of) the firstRFID reader. The map may show RFID reader(s) that may be adjacent to thefirst RFID reader. The second RFID reader may be an adjacent RFID readerand may be accordingly identified.

At operation 508, the computer system may determine whether the secondread event may be a relevant read event. A read event may be relevantwhen indicating a potential cross-read. Accordingly, the second readevent may be relevant based on a number of factors. These factors mayinclude the adjacency between the first RFID reader and the second RFIDreader, an overlap between the respective zones, the first and secondread events identifying the same item, and/or the first and second readevents being generated within the predefined amount of time from eachother. For instance, if the second read event identifies the item andwas generated during a read cycle that overlaps with the read cycle ofthe first read event, the computer system may determine that the secondread event is relevant. If so, operation 510 may be performed to analyzemultiple parameters across the first and second read events and mitigatethe risk of cross-read. Otherwise, operation 512 may be performed.

At operation 510, the computer system may determine the location of theitem based on at least two parameters from the first event and at leasttwo parameters from the second event. As described herein above, thecomputer system may implement a statistical analysis to generate scores.The scores may be compared to make the determination. A further examplestatistical analysis is illustrated in FIG. 6.

At operation 512, the computer system may determine the location of theitem based on the first read event and independently of the second readevent. That may be the case because at operation 506, the computersystem may have determined that the second read event may not berelevant. Accordingly, the computer system may use any of the firstcount, the first average signal strength, the first maximum signalstrength, and/or the first set of time stamps to determine that duringthe first read cycle, the item may be closest to the first RFID reader.

FIG. 6 illustrates an example statistical analysis of multipleparameters across multiple read events. The example flow may start atoperation 602, where the computer system may access at least twoparameters from the first read event. For example, the first count, thefirst average signal strength, and the first maximum signal strength maybe accessed by parsing fields of the first read event.

At operation 604, the computer system may generate, for some or all ofthe accessed parameters, an individual score based on the parameters andthe corresponding parameters from the second read event. An individualscore for a first parameter from the first read event may be anormalized parameter given the first parameter and given thecorresponding second parameter from the second read event. For instance,the individual score may be a normalized count, a normalized averagesignal strength, and/or a normalized maximum signal strength.

At operation 606, the computer system may generate a first score for thefirst read event. For example, the computer system may sum theindividual scores generated at operation 604. In an example, the firstscore may represent the sum of the normalized count, the normalizedaverage signal strength, and/or the normalized maximum signal strength.

At operation 608, the computer system may determine whether the firstscore and a second score generated for the second event fall within athreshold amount of each other. The second score may be similarlygenerated for the second read event based on the parameters of thesecond read event. The threshold amount may be a predefined deviation.If the difference between the two scores is too large (e.g., exceedingthe threshold amount), operation 610 may be performed, where thecomputer system may rely on one of the two scores to make the locationdetermination. Otherwise, operation 612 may be performed, where thecomputer system may rely on additional parameters to make the locationdetermination.

At operation 610, the computer system may determine the location of theitem based on the first score or the second score. For instance, thelarger score of the two may be selected. The RFID reader having thatscore may be selected as being closest to the item.

At operation 612, the computer system may access additional parametersfrom the first read event and the second read event. In an example, theadditional parameter may not have been considered in the analysis sofar.

At operation 614, the computer system may update the first score and thesecond score based on the additional parameters. The update may involveperforming operations 604-608 in light of the additional parameters. Forexample, if maximum signal strength may not have been analyzed, thisparameter may be accessed from both read events. Each of the scores maybe updated accordingly and compared.

At operation 616, the computer system may not update the first andsecond scores. Instead, the computer system may make the locationdetermination based on a comparison of the additional parameters. Forinstance, the computer system may access time stamps from both events(e.g., the last time stamp from the first read event and the last timestamp from the second read event). The accessed time stamps may becompared to generate a timing order. The computer system may make thelocation determination based on the timing order (e.g., may select theRFID reader that has the latest time stamp).

FIG. 7 illustrates example end-to-end architecture of a computingenvironment for processing RFID read events. RFID read events may begenerated by RFID readers and processed by a computer system. Suchcomponents may implement part of the computing environment to facilitatetracking of items in a sortation facility. The items may be availablefor purchase from an electronic marketplace associated with thesortation facility. The service provider may implement a tracking moduleto track the items. The items may be listed for offering by a seller 710and/or the service provider and may be available for ordering by acustomer 760.

In a basic configuration, the seller 710 may utilize a seller device 712to access local applications, a web service application 720, a selleraccount accessible through the web service application 720, a web siteor any other network-based resources via one or more networks 780. Insome aspects, the web service application 720, the web site, and/or theseller account may be hosted, managed, and/or otherwise provided by oneor more computing resources of the service provider, such as byutilizing one or more service provider devices 730. The seller 710 mayuse the local applications and/or the web service application 720 tointeract with the network-based resources of the service provider andperform seller-related transactions. These transactions may include, forexample, offering items for sale.

In some examples, the seller device 712 may be any type of computingdevices such as, but not limited to, a mobile phone, a smart phone, apersonal digital assistant (PDA), a laptop computer, a thin-clientdevice, a tablet PC, etc. In one illustrative configuration, the sellerdevice 712 may contain communications connection(s) that allow theseller device 712 to communicate with a stored database, anothercomputing device or server, seller terminals, and/or other devices onthe networks 780. The seller device 712 may also include input/output(I/O) device(s) and/or ports, such as for enabling connection with akeyboard, a mouse, a pen, a voice input device, a touch input device, adisplay, speakers, a printer, etc.

The seller device 712 may also include at least one or more processingunits (or processor device(s)) 714 and at least one memory 716. Theprocessor device(s) 714 may be implemented as appropriate in hardware,computer-executable instructions, firmware, or combinations thereof.Computer-executable instructions or firmware implementations of theprocessor device(s) 714 may include computer-executable ormachine-executable instructions written in any suitable programminglanguage to perform the various functions described.

The memory 716 may store program instructions that are loadable andexecutable on the processor device(s) 714, as well as data generatedduring the execution of these programs. Depending on the configurationand type of seller device 712, the memory 716 may be volatile (such asrandom access memory (RAM)) and/or non-volatile (such as read-onlymemory (ROM), flash memory, etc.). The seller device 712 may alsoinclude additional storage, which may include removable storage and/ornon-removable storage. The additional storage may include, but is notlimited to, magnetic storage, optical disks, and/or tape storage. Thedisk drives and their associated computer-readable media may providenon-volatile storage of computer-readable instructions, data structures,program modules, and other data for the computing devices. In someimplementations, the memory 716 may include multiple different types ofmemory, such as static random access memory (SRAM), dynamic randomaccess memory (DRAM), or ROM.

Turning to the contents of the memory 716 in more detail, the memory mayinclude an operating system (O/S) 718 and the one or more applicationprograms or services for implementing the features disclosed hereinincluding the web service application 720. In some examples, the sellerdevice 712 may be in communication with the service provider devices 730via the networks 780, or via other network connections. The networks 780may include any one or a combination of many different types ofnetworks, such as cable networks, the Internet, wireless networks,cellular networks, and other private and/or public networks. While theillustrated example represents the seller 710 accessing the web serviceapplication 720 over the networks 780, the described techniques mayequally apply in instances where the seller 710 interacts with theservice provider devices 730 via the seller device 712 over a landlinephone, via a kiosk, or in any other manner. It is also noted that thedescribed techniques may apply in other client/server arrangements(e.g., set-top boxes, etc.), as well as in non-client/serverarrangements (e.g., locally stored applications, peer-to-peer systems,etc.).

Similarly, a customer 760 may utilize customer device 762 to accesslocal applications, a web service application 770 (or some other mobileapplication such as a “mobile app” available from an application store),a customer account accessible through the web service application 770, aweb site, or any other network-based resources via the networks 780. Insome aspects, the web service application 770, the web site, and/or theuser account may be hosted, managed, and/or otherwise provided by theservice provider devices 730 and may be similar to the web serviceapplication 720, the web site accessed by the computing device 712,and/or the seller account, respectively.

The customer 760 may use the local applications and/or the web serviceapplication 770 to conduct transactions with the network-based resourcesof the service provider. These transactions may include, for example,browsing for items, viewing items, ordering items, tracking shippingprogress, and/or other transactions.

In some examples, the customer device 762 may be configured similarly tothe seller device 712 and may include at least one or more processingunits (or processor device(s)) 764 and at least one memory 766. Theprocessor device(s) 764 may be implemented as appropriate in hardware,computer-executable instructions, firmware, or combinations thereofsimilarly to the processor device(s) 714. Likewise, the memory 766 mayalso be configured similarly to the memory 716 and may store programinstructions that are loadable and executable on the processor device(s)764, as well as data generated during the execution of these programs.For example, the memory 766 may include an operating system (O/S) 768and the one or more application programs or services for implementingthe features disclosed herein including the web service application 770.

As described briefly above, the web service applications 720 and 770 mayallow the seller 710 and customer 760, respectively, to interact withthe service provider devices 730 to conduct transactions involvingitems. The service provider devices 730, perhaps arranged in a clusterof servers or as a server farm, may host the web service applications720 and 770. These servers may be configured to host a web site (orcombination of web sites) viewable via the computing devices 712 and762. Other server architectures may also be used to host the web serviceapplications 720 and 770. The web service applications 720 and 770 maybe capable of handling requests from many sellers 710 and customers 760,respectively, and serving, in response, various interfaces that may berendered at the computing devices 712 and 762 such as, but not limitedto, a web site. The web service applications 720 and 770 may interactwith any type of web site that supports interaction, including socialnetworking sites, electronic retailers, informational sites, blog sites,search engine sites, news and entertainment sites, and so forth. Asdiscussed above, the described techniques may similarly be implementedoutside of the web service applications 720 and 770, such as with otherapplications running on the computing devices 712 and 762, respectively.

The service provider devices 730 may, in some examples, providenetwork-based resources such as, but not limited to, applications forpurchase and/or download, web sites, web hosting, client entities, datastorage, data access, management, virtualization, etc. The serviceprovider devices 730 may also be operable to provide web hosting,computer application development, and/or implementation platforms, orcombinations of the foregoing to the seller 710 and customer 760.

The service provider devices 730 may be any type of computing devicesuch as, but not limited to, a mobile phone, a smart phone, a personaldigital assistant (PDA), a laptop computer, a desktop computer, a servercomputer, a thin-client device, a tablet PC, etc. The service providerdevices 730 may also contain communications connection(s) that allowservice provider devices 730 to communicate with a stored database,other computing devices or servers, seller terminals, and/or otherdevices on the network 780. The service provider devices 730 may alsoinclude input/output (I/O) device(s) and/or ports, such as for enablingconnection with a keyboard, a mouse, a pen, a voice input device, atouch input device, a display, speakers, a printer, etc.

Additionally, in some embodiments, the service provider devices 730 maybe executed by one or more virtual machines implemented in a hostedcomputing environment. The hosted computing environment may include oneor more rapidly provisioned and released network-based resources. Suchnetwork-based resources may include computing, networking, and/orstorage devices. A hosted computing environment may also be referred toas a cloud computing environment. In some examples, the service providerdevices 730 may be in communication with the computing devices 712 and762 via the networks 780, or via other network connections. The serviceprovider devices 730 may include one or more servers, perhaps arrangedin a cluster, or as individual servers not associated with one another.

In one illustrative configuration, the service provider devices 730 mayinclude at least one or more processing units (or processor devices(s))732 and at least one memory 734. The processor device(s) 732 may beimplemented as appropriate in hardware, computer-executableinstructions, firmware, or combinations thereof. Computer-executableinstruction or firmware implementations of the processor device(s) 732may include computer-executable or machine-executable instructionswritten in any suitable programming language to perform the variousfunctions described.

The memory 734 may store program instructions that are loadable andexecutable on the processor device(s) 732, as well as data generatedduring the execution of these programs. Depending on the configurationand type of the service provider devices 730, the memory 734 may bevolatile (such as random access memory (RAM)) and/or non-volatile (suchas read-only memory (ROM), flash memory, etc.). The service providerdevices 730 may also include additional removable storage and/ornon-removable storage including, but not limited to, magnetic storage,optical disks, and/or tape storage. The disk drives and their associatedcomputer-readable media may provide non-volatile storage ofcomputer-readable instructions, data structures, program modules, andother data for the computing devices. In some implementations, thememory 734 may include multiple different types of memory, such asstatic random access memory (SRAM), dynamic random access memory (DRAM),or ROM.

Additionally, the computer storage media described herein may includecomputer-readable communication media such as computer-readableinstructions, program modules, or other data transmitted within a datasignal, such as a carrier wave, or other transmission. Such atransmitted signal may take any of a variety of forms including, but notlimited to, electromagnetic, optical, or any combination thereof.However, as used herein, computer-readable media does not includecomputer-readable communication media.

Turning to the contents of the memory 734 in more detail, the memory mayinclude an operating system (O/S) 736, code for an electronicmarketplace 738 and code for a tracking module 740. The tracking module740 may be configured to track items based on RFID read events andprovide information about the tracking via interfaces to the serviceprovider, the seller device 712, and the customer device 762.

The specification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense. It will, however, beevident that various modifications and changes may be made thereuntowithout departing from the broader spirit and scope of the disclosure asset forth in the claims.

Other variations are within the spirit of the present disclosure. Thus,while the disclosed techniques are susceptible to various modificationsand alternative constructions, certain illustrated embodiments thereofare shown in the drawings and have been described above in detail. Itshould be understood, however, that there is no intention to limit thedisclosure to the specific form or forms disclosed, but on the contrary,the intention is to cover all modifications, alternative constructionsand equivalents falling within the spirit and scope of the disclosure,as defined in the appended claims.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the disclosed embodiments (especially in thecontext of the following claims) are to be construed to cover both thesingular and the plural, unless otherwise indicated herein or clearlycontradicted by context. The terms “comprising,” “having,” “including,”and “containing” are to be construed as open-ended terms (i.e., meaning“including, but not limited to,”) unless otherwise noted. The term“connected” is to be construed as partly or wholly contained within,attached to, or joined together, even if there is something intervening.Recitation of ranges of values herein are merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range, unless otherwise indicated herein, and eachseparate value is incorporated into the specification as if it wereindividually recited herein. All methods described herein may beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate embodiments of the disclosure anddoes not pose a limitation on the scope of the disclosure unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe disclosure.

Disjunctive language such as that included in the phrase “at least oneof X, Y, or Z,” unless specifically stated otherwise, is otherwiseunderstood within the context as used in general to present that anitem, term, etc., may be either X, Y, or Z, or any combination thereof(e.g., X, Y, and/or Z). Thus, such disjunctive language is not generallyintended to, and should not, imply that certain embodiments require atleast one of X, at least one of Y, or at least one of Z each to bepresent.

Preferred embodiments of this disclosure are described herein, includingthe best mode known to the inventors for carrying out the disclosure.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the disclosure to be practicedotherwise than as specifically described herein. Accordingly, thisdisclosure includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the disclosure unlessotherwise indicated herein or otherwise clearly contradicted by context.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

What is claimed is:
 1. A system, comprising: a first radio frequencyidentification (RFID) reader located within a first zone and configuredto generate a first read event based at least in part on one or morefirst reads of an RFID tag during a first read cycle of the first RFIDreader, the RFID tag attached to an item having a variable location overtime, the first read event identifying the RFID tag and comprising firstRFID parameters, the first RFID parameters comprising a first count oftimes the RFID tag was read, a first average signal strength, a firstmaximum signal strength, and a first set of time stamps; a second RFIDreader located within a second zone and configured to generate a secondread event based at least in part on one or more second reads of theRFID tag during a second read cycle of the second RFID reader, thesecond read event identifying the RFID tag and comprising second RFIDparameters, the second RFID parameters comprising a second count oftimes the RFID tag was read, a second average signal strength, a secondmaximum signal strength, and a second set of time stamps; a processor;and a memory comprising computer-readable instructions that, uponexecution by the processor, cause the computer system to at least:receive the first read event from the first RFID reader and the secondread event from the second RFID reader; determine whether a time overlapexists between the first read event and the second read event based atleast in part on the first read cycle and the second read cycle; basedat least in part on determining that the time overlap exists, store anassociation between the item and one of the first zone or the secondzone based at least in part on two or more first RFID parameters fromthe first read event and two or more second RFID parameters from thesecond read event; and provide an indication of the association to adevice for presentation at the device.
 2. The system of claim 1, whereinthe computer-readable instructions cause the computer to store theassociation between the item and one of the first zone or the secondzone by acts that include: generating a total count based at least inpart on the first count and the second count; generating a total averagesignal strength based at least in part on the first average signalstrength and the second average signal strength; generating a totalmaximum signal strength based at least in part on the first maximumsignal strength and the second maximum signal strength; for each of thefirst read event and the second read event, generating a score based atleast in part on the total count, the total average signal strength, andthe total maximum signal strength; and determining whether the item islocated within the first zone or the second zone based at least in parton a comparison of the score of the first read event and the score ofthe second read event.
 3. The system of claim 2, wherein thecomputer-readable instructions cause the computer to determine whetherthe item was located within the first zone or the second zone by actsthat include: determining that the scores of the first read event andthe second read event are within a threshold amount from each otherbased at least in part on the comparison; comparing a first time stampfrom the first set of time stamps and a second time stamp from thesecond set of time stamps based at least in part on the scores beingwithin the threshold amount; determining a timing order between thefirst time stamp and the second time stamp; and determining whether theitem is located within the first zone or the second zone based at leastin part on the timing order.
 4. The system of claim 1, wherein the firstzone and the second zone are located within a sortation facility,wherein the variable location varies with movement of the item withinthe sortation facility, and the instructions further cause the computersystem to at least identify, at a user interface, the first zone and thesecond zone relative to the sortation facility and the associationbetween the item and the one of the first zone or the second zone.
 5. Acomputer-implemented method comprising: accessing, by a computer system,a first read event generated by a first radio frequency identification(RFID) reader located within a first zone, the first read eventidentifying an RFID tag associated with an item and comprising firstRFID parameters, and generated at a first time; accessing, by thecomputer system, a second read event generated by a second RFID readerlocated within a second zone, the second read event identifying the RFIDtag and comprising second RFID parameters, and generated at a secondtime, the first time and the second time being within a predefinedamount of time of each other; and storing, by the computer system, anassociation between a location of the item and one of the first zone orthe second zone based at least in part on two or more first RFIDparameters from the first read event and two or more second RFIDparameters from the second read event.
 6. The computer-implementedmethod of claim 5, further comprising presenting, at a user interface,the location of the item within a sortation facility within which thefirst RFID reader and the second RFID reader are located; and generatingeach read event during a read cycle, wherein the first RFID parametersand the second RFID parameters each comprise a count of times the RFIDtag was read, an average signal strength, a maximum signal strength, anda set of time stamps, wherein the predefined amount of time represents atime overlap between the first read event and the second read event. 7.The computer-implemented method of claim 5, wherein storing theassociation between the location of the item and the one of the firstzone or the second zone comprises determining whether the location ofthe item falls within the first zone or the second zone based at leastin part on a normalization of the two or more first RFID parameters fromthe first read event and the two or more second RFID parameters from thesecond read event.
 8. The computer-implemented method of claim 5,wherein storing the association between the location of the item and theone of the first zone or the second zone comprises: generating a firstscore for the first read event based at least in part on the two or morefirst RFID parameters from the first read event and the two or moresecond RFID parameters from the second read event; and determiningwhether the location of the item falls within the first zone or thesecond zone based at least in part on a comparison of the first scoregenerated for the first read event to a second score generated for thesecond read event.
 9. The computer-implemented method of claim 8,wherein generating the first score comprises: for each of the two ormore first RFID parameters from the first read event, generating anindividual score based at least in part on a respective one of the firstRFID parameters from the first read event and a corresponding one of thesecond RFID parameters from the second read event; and generating thefirst score based at least in part on the individual scores of the twoor more first RFID parameters from the first read event.
 10. Thecomputer-implemented method of claim 8, wherein generating the firstscore comprises: generating, from the first read event and the secondread event, a total count of times the RFID tag was read, an averagesignal strength, and a maximum signal strength.
 11. Thecomputer-implemented method of claim 10, wherein generating the firstscore comprises: dividing a first count of times the RFID tag was readfrom the first read event by the total count to generate a normalizedcount; dividing a first average signal strength from the first readevent by the average signal strength to generate a normalized averagesignal strength; dividing a first maximum signal strength from the firstread event by the maximum signal strength to generate a normalizedmaximum signal strength; and summing the normalized count, thenormalized average signal strength, and the normalized maximum signalstrength to generate the first score.
 12. The computer-implementedmethod of claim 11, wherein determining whether the location of the itemfalls within the first zone or the second zone comprises determiningthat the location of the item falls within the first zone based at leastin part on a determination that the first score is greater than thesecond score.
 13. The computer-implemented method of claim 12, wherein,based at least in part on a comparison indicating that a differencebetween the first score and the second score is within a thresholdamount, comparing a last time stamp from the first read event to a lasttime stamp from the second read event.
 14. The computer-implementedmethod of claim 13, wherein determining whether the location of the itemfalls within the first zone or the second zone comprises determiningthat the location of the item falls within the first zone based at leastin part on the last time stamp from the first read event being morerecent than the last time stamp from the second read event.
 15. Thecomputer-implemented method of claim 5, further comprising: accessing,by the computer system, a third read event generated by a third RFIDreader located within a third zone, the third read event identifying theRFID tag and comprising third RFID parameters, and storing, by thecomputer system, an association between the location of the item and thethird zone based at least in part on two or more third RFID parametersfrom the third read event.
 16. One or more computer-readable storagemedia comprising instructions that, upon execution by a processor, causea system to perform operations comprising: accessing a first read eventgenerated by a first radio frequency identification (RFID) readerlocated within a first zone, the first read event identifying an RFIDtag associated with an item and comprising first RFID parameters, thefirst RFID parameters comprising a first count of times the RFID tag wasread, a first average signal strength, a first maximum signal strength,and a first set of time stamps; accessing a second read event generatedby a second RFID reader located within a second zone, the second readevent identifying the RFID tag and comprising second RFID parameters,the second RFID parameters comprising a second count of times the RFIDtag was read, a second average signal strength, a second maximum signalstrength, and a second set of time stamps; determining whether a timeoverlap exists between the first read event and the second read event;and based at least in part on determining that the time overlap exists,storing an association between the item and one of the first zone or thesecond zone based at least in part on two or more first RFID parametersfrom the first read event and two or more second RFID parameters fromthe second read event.
 17. The system of claim 16, wherein the one ormore computer-readable storage media comprising instructions that, uponexecution by a processor, cause the system to receive the first readevent and the second read event from the first RFID reader and thesecond RFID reader, respectively, at least in part via a pushcommunication mechanism.
 18. The system of claim 16, wherein the one ormore computer-readable storage media comprising instructions that, uponexecution by a processor, cause the system to access the first readevent and the second read event at least in part via a mapping of RFIDreaders to respective locations, wherein the mapping indicates that thefirst RFID reader is located within the first zone, the second RFIDreader is located within the second zone, and the first zone and thesecond zone are adjacent.
 19. The system of claim 18, wherein accessingthe first read event comprises receiving the first read event from thefirst RFID reader, and wherein the operations further comprise:determining that the second zone is adjacent to the first zone based atleast in part on the mapping; and accessing the second read event basedat least in part on the first read event being received and the secondzone being adjacent to the first zone.
 20. The system of claim 16,wherein the one or more computer-readable storage media comprisinginstructions that, upon execution by a processor, cause the system toaccess the first read event and the second read event in real time, andwherein storing the association comprises determining in real timewhether the item is located in the first zone or the second zone, andwherein the operations further comprise presenting a location of theitem at a user interface in real time.